1. Field of the Invention
The present invention relates to a method for reducing inter-beam interference generated when forming a multiple beam in a wireless communication system, and a method for transmitting/receiving a signal using the same.
2. Related Art
In recent years, as supply and use of mobile devices such as a smart phone and a tablet personal computer (PC) have increased, there is a need for a wireless communication system capable of supporting a plurality of users and obtaining a high transmission rate. To this end, researches and studies have been performed toward a technology of using multiple beams in the same channel. Further, in order to ensure a wide bandwidth, a transmission frequency has been gradually increased to a millimeter wave band. Since the millimeter wave has strong straightness, the millimeter wave is used in a line of sight (LOS) environment, and a small number of the millimeter wave may be reflected, diffracted, and transmitted. For this reason, there is greatly growing interest in a multiple beam antenna technology in the millimeter wave band.
FIG. 1 is a diagram illustrating a cell concept in a base station according to the related art, and FIG. 2 is a diagram illustrating a cell concept of a base station when using multiple beams in the same channel.
In the base station according to the related art, as shown in FIG. 1, when a wave propagation reach zone (hereinafter referred to as ‘cell’) is displayed as a circle based on the base station, the cell of 360° is divided into three sectors in a unit of 120° and a signal is fully radiated to each sector using an antenna having a beam width of 120°. In this case, in order to reduce interference between sectors, different frequency bands are allocated to sectors, respectively. In addition, similar to the interference between cells, each base station selects different frequencies with respect to a cell overlapping with a neighboring cell. For example, FIG. 1 illustrates a case where a first base station BS1 allocates a first frequency band f1 to a first sector sector1 and a second base station BS3 allocates a third frequency band f3 to a third sector sector3 as the first sector sector1 of the first base station BS1 overlaps with the third sector sector3 of the third base station BS4.
However, when multiple beams are formed in the same channel (that is, the same frequency band), as shown in FIG. 2, each sector is divided into M×N (here, M and N are a natural number) sub-sectors, and a beam corresponding to a specific sub-sector is formed in a terminal located in the specific sub-section.
For example, Korean Patent Publication No. 10-2014-0056561 (published on May 12, 2014) discloses a method for operation of a terminal and a base station in a cellular telecommunication system operating multiple beams. In the method for operation of a terminal and a base station in a cellular telecommunication system operating multiple beams, a plurality of beams are formed, beam identifiers are allocated to the plurality of beams, respectively. After the beam identifiers corresponding to the beams are transmitted using each beam, the beam identifier of the beam selected by the terminal is received from the terminal.
However, since the above method using the multiple beams forms the same number of beams as that of users, a high communication rate may be provided to the users. However, when the inter-beam interference is great, a bad performance is represented as compared with the related art.